System and method for removing gases from liquid transport systems

ABSTRACT

A liquid transport system. The liquid transport system includes a gas displacement piping section fluidly coupled to a centrifugal pump or to other portions of the liquid transport system. The gas displacement piping section includes an inlet, and outlet and a gas discharge located between the inlet and outlet for enabling gases to escape or be displaced from the gas displacement piping section, the gas displacement piping section being configured to cause entrained gases in flowing liquid to migrate toward the gas discharge. In centrifugal pump embodiments, the gas displacement piping section may be fluidly coupled upstream or downstream of the centrifugal pump, and may include a vacuum pump and/or float valve coupled to the gas discharge.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit under 35 U.S.C. § 119(e) of the following U.S. provisional patent application, which is incorporated herein by reference in its entirety for all purposes: Ser. No. 60/533,909, filed Dec. 31, 2003.

BACKGROUND

Centrifugal pumps are commonly used for liquid transport, and are widely employed in irrigation, domestic water systems, sewage handling and many other applications. Liquid is urged through the pump by a spinning disk-shaped impeller positioned inside an annular volute. The volute has an eye at the center where liquid enters the pump and is directed into the center of the impeller. The rotation of the impeller flings the liquid outward to the perimeter of the impeller where it is collected for tangential discharge.

One limitation of centrifugal pumps is their limited ability to draw fluid for priming when starting from an air-filled or dry condition. The impeller, which is designed to pump liquids, cannot generate sufficient vacuum when operating in air to draw liquid up to the pump when the standing level of the liquid is below the eye of the impeller. Once the liquid reaches the eye, the outward motion of the liquid away from the eye creates the conditions necessary to draw a continuing stream of liquid.

Gases may be present in liquid pipelines for various different reasons. Gases can arise, for example, as a result of air leaks in piping systems. Turbulence, chemical reactions and other causes can also result in gases becoming entrained or otherwise trapped in pipelines. In liquid pipelines used with pumps, leftover air may be present or accumulate in the inlet suction line, even after priming. In these and other settings, removal of gas from the pipeline will at times be desirable and/or necessary. For example, excess entrained air can adversely affect the performance of a centrifugal pump.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a liquid transport system according to the present description, including a centrifugal pump and a gas displacement piping section fluidly coupled to the centrifugal pump.

FIG. 2 depicts a vacuum pump assembly that may be employed in connection with the liquid transport system of FIG. 1 or other gas displacement piping section embodiments.

FIGS. 3-8 depict various alternate embodiments of gas displacement piping sections according to the present description.

DETAILED DESCRIPTION

The present disclosure is directed to a system and method for removing air and other gases from a liquid-filled pipeline or other liquid transport system. In the following description and accompanying figures, certain exemplary embodiments will be referred to as an air scavenger system and/or air scrubbing system. The described systems and methods may be advantageously employed in pumping systems and other systems in which unwanted gases are found in liquid pipelines. Gases may arise in such systems due to various circumstances, including air leaks, initial conditions (e.g., an air-filled pump inlet prior to priming, turbulence, chemical reactions, etc.)

FIG. 1 depicts a pump system 20 according to the present description. Pump system 20 may include a motor 22, centrifugal section 24 and a float valve assembly 26. The centrifugal section includes an input 28 leading to an eye 32 of an impeller 40 disposed inside volute 34. Volute 34 has an output 36 to which is connected a piping system or check valve 38 to prevent reverse flow when the pump is priming or idle. Impeller 40 is mounted inside the volute on an impeller shaft 42, which is driven by motor 22. A combustion motor may be used in certain applications, although electric or other types of motors may be employed. A drive end of impeller shaft 42 is operatively connected to motor 22, while an impeller end is operatively connected to impeller 40.

Pump system 20 is configured so that rotation of impeller 40 causes fluid to be drawn into impeller eye 32 and expelled out through output 36. During startup and at other times, it will often be desirable to prime the pump system or otherwise cause air or trapped gases to be removed from piping sections or other liquid-carrying portions of the system.

FIG. 2 depicts a vacuum pump assembly 50 which may be coupled with float valve assembly 26 or other portions of pump system 20 in order to remove air or other unwanted gases from liquid-carrying portions of the system. In the depicted example, vacuum pump assembly 50 includes a vacuum pump motor 52 via a rotating shaft and mechanical linkage to a diaphragm or diaphragms 54. Diaphragm 54 reciprocates up and down during operation to draw air through vacuum input 56, and force the drawn air out through exhaust 58. A check valve system 60 is provided in connection with diaphragm 54 to prevent reverse airflow.

In the depicted exemplary embodiment, vacuum pump input 56 (e.g., a hose) is coupled to float valve assembly 26. The vacuum pump assembly may be operated during startup or at other times to cause air or other gases to be drawn out of piping section 80. The withdrawn air flows through float valve assembly 26 and vacuum input 56, and is expelled out through vacuum pump exhaust 58. When the pump has been primed (i.e., little or no air remains in piping section 80), continued suction created by vacuum pump assembly 50 may cause liquid to rise within float valve assembly 26. Rising liquid levels cause a float to rise within the float valve assembly. Once the float rises to a certain predetermined level, the float causes a float valve to close, cutting off the fluid coupling between the float valve assembly and vacuum pump assembly. This closing of the float valve prevents liquid from reaching the vacuum pump. In addition, closing of the float valve may be used to trigger automatic shutoff of the vacuum pump (e.g., by turning off vacuum pump motor 52). Vacuum pump assembly 50 may be otherwise configured so that its operation (e.g., turning on/off) is controlled by the status of the float valve and/or conditions existing in the valve chamber or scavenger pipe. Additionally, or alternatively, a valve system may be employed having a solenoid valve that opens when air is sensed in the valve chamber and closes when the air has been removed.

In certain alternate embodiments, vacuum pump assembly 50 may be operatively coupled with impeller shaft 42 and/or motor 22, so that the vacuum pump is driven off the pump itself, thereby eliminating the need for a separate vacuum pump motor (e.g., motor 52). In addition, various lubrication systems may be employed within vacuum pump assembly 50 and other parts of pump system 20 to facilitate operation. Examples of pump systems employing various priming configurations, and valve and lubrication systems may be found in U.S. Pat. No. 6,575,706, issued Jun. 10, 2003, which is hereby incorporated by this reference, in its entirety and for all purposes.

Referring still to FIG. 1, piping section 80 may be referred to as an air scavenger pipe or suction spool. Whether used in connection with the float valve and vacuum pump or in other parts of pump system 20, piping section 80 may be specially configured to facilitate displacement or removal of air or other gases. The gases typically are displaced by using a pressure differential (e.g., such as created by the vacuum pump) to cause the gas to be withdrawn via an opening in the side of the scavenger pipe. Alternatively, in a pressurized pipeline, the vacuum pump may be removed from the system as the pressure differential between the pipeline and the outside air will cause gases in the pipeline to be automatically expelled from the system using an automatic float valve.

As in the depicted example, a typical use of the air scavenger system is to remove gases from a suction pipe (e.g., piping section 80) prior to a pump. Removal of gases in piping that is upstream of the pump can aid in priming and/or improve performance of the pump. Indeed, in some settings, entrained air can severely hamper pump performance if not removed. The air removal systems and methods of the present disclosure can be used in various different types of pumps, including pumps having horizontal, vertical or other orientations. The scavenger pipe may be located in any desirable location within the fluid transport system connected to the pump, including upstream or downstream of the pump. When priming a vertically mounted pump with the air scavenger system, the float valve may be elevated above the height of the pump and a suction hose connected between the pump and the float valve, or air scavenger pipe, to insure that the air is removed from the pump as well as the scavenger pipe.

The air scavenger pipe may take many forms. In typical configurations, the air scavenger pipe has an inlet, an outlet and one or more openings in the top of the pipe where the float valve assembly is attached. Gases in the pipeline may be removed via the opening or openings in the top of the air scavenger pipe.

In the example of FIGS. 1 and 3, piping section 80 has a straight cylindrical configuration. It will be desirable in many settings, however, to employ other shapes. In particular, testing has demonstrated that varying the velocity of fluid between the inlet and the area where gas is to be withdrawn facilitates gas displacement. FIGS. 4-7 depict various alternate embodiments of an air scavenger pipe that may be used to create pressure/velocity differentials in liquid flow. Each figure includes respective side and top views of the piping section.

The variation in cross-sectional area may be accomplished by expanding or contracting the pipe in any direction and/or region. In piping with a round cross section, these non-cylindrical areas may be referred to as eccentric regions, such that the scavenger pipe may be eccentric on the top, bottom, sides, etc. In sewage and other pumping applications, it will often be preferable to expand horizontally on the sides of the air scavenger pipe (“side eccentric”), while maintaining the top and bottom of the air scavenger pipe at the same height throughout the transition from inlet to outlet of the air scavenger pipe. This shape may in certain settings prevent unwanted settling of debris or other material. For example, sewage may contain materials that are heavier or lighter than water, such that those materials could tend to settle out in lower or higher sections of scavenger pipe.

In typical sewage handling applications, the air scavenger pipe has equal cross-sectional areas at the inlet and outlet and a larger cross-sectional middle section. The inlet and outlet cross-sectional areas will often be the same because a typical sewage pipeline has a constant diameter throughout its length in the areas where the air scavenger system is likely to be installed. It should be appreciated, however, that the inlet and outlet may be sized differently.

In an alternate configuration, the inlet of the air scavenger pipe may have a larger cross-sectional area than the outlet. The transition to the smaller piping may be accomplished in various ways, though one common approach is to maintain the top horizontal, while tapering along the bottom of the pipe moving toward the outlet.

Referring first to the example of FIG. 4, piping section 100 has a cross-sectional area that increases from inlet 102 to outlet 104. This variation in area causes flowing liquid to slow down after passing through inlet 102. Accordingly, when the liquid passes by gas discharge 106 (which may be coupled to atmosphere or to a float valve and vacuum pump), the reduced velocity may increase the ability to remove entrained or other unwanted gases. In particular, the reduced velocity can allow entrained gases to migrate to the top of the piping section to be expelled or drawn through gas discharge 106.

Gas discharge 106 may be formed as a single opening or, as in the present example, a group of elongate openings or slots 108. In the depicted embodiment, slots 108 are oriented perpendicularly to the direction of flow. As shown in the figure, debris bars 110 or like structures may be disposed on the inside of the pipe wall over slots 108, to create a mesh-like arrangement for preventing debris from escaping out of the pipe. It will be appreciated that any practicable number of slots and/or debris bar structures may be employed, in various different orientations and configurations.

FIGS. 5-7 depict alternate embodiments of a scavenger pipe having inlets 120 and outlets 122 of equal cross-sectional areas, but with larger intervening regions 124 to provide reduced velocity of flow. Piping section 140 (FIG. 5) is bulged outward on an upper portion of the pipe near gas discharge 142. Piping section 160 (FIG. 6) is bulged outward on a bottom region opposite gas discharge 162. Piping section 180 (FIG. 7) is bulged outward on the sides of the pipe between the inlet and outlet, to either side of gas discharge 182.

FIG. 8 depicts a structure, such as vane assembly 200, which may be affixed to the inlet of a piping section to further facilitate withdrawal of unwanted gases. Vane assembly 200 may be affixed to a scavenger pipe (typically on the inlet side), and includes one or more protrusions or vanes 202. The vanes extend inward to disrupt the liquid flow. This disruption can cause gas to come out of solution, or otherwise create flow disturbances that increase the ability to remove gas from the downstream section of piping. Assembly 200 may be employed in connection with a variety of gas-removal systems, including any of the scavenger pipe embodiments described herein.

The gas discharge on any of the described scavenger pipes may take numerous different configurations. For example, gas discharge 142 (FIG. 5) has elongate slots 144 oriented parallel to the flow direction. Gas discharge 162 (FIG. 6) has elongate slots 164 oriented at an angle to the flow direction. In these and other elongate slot configurations, an additional structure may be employed to create a debris-retaining mesh, as previously discussed with reference to FIG. 4. Alternatively, the piping section itself may be formed to create a mesh or other configuration that allows gas displacement while preventing escape of debris. For example, gas discharge 182 (FIG. 7) includes a plurality of circular holes 184 formed in the wall of piping section 180, with the holes being sized to retain debris.

While various alternative embodiments and arrangements of an air removal system and method have been shown and described herein, it will be appreciated that numerous other embodiments, arrangements, and modifications are possible and are within the scope of the disclosure. The description herein should be understood to include all novel and non-obvious combinations of elements described herein, and claims may be presented in this or a later application to any novel and non-obvious combination of these elements. The embodiments herein are illustrative, and no single feature or element is essential to all possible combinations that may be claimed in this or a later application. 

1. A liquid transport system, comprising: a piping system configured to transport pressurized liquid; a gas displacement piping section, including: an inlet coupled to a first portion of the piping system; an outlet coupled to a second portion of the piping system; and an intervening region of larger cross-sectional area than the inlet, a gas discharge being located on an upper portion of the intervening region.
 2. The system of claim 1, further comprising a centrifugal pump, where the gas displacement piping section is coupled upstream of the centrifugal pump to an input of the centrifugal pump.
 3. The system of claim 2, further comprising a vacuum pump fluidly coupled with the gas discharge of the gas displacement piping section.
 4. The system of claim 3, further comprising a float valve coupled between the gas discharge of the gas displacement piping section and the vacuum pump.
 5. The system of claim 4, where the gas displacement piping section increases in cross-sectional area from the inlet to the outlet.
 6. The system of claim 4, where the inlet and the outlet of the gas displacement piping section are smaller in cross-sectional area than the intervening region.
 7. The system of claim 1, further comprising a vacuum pump fluidly coupled with the gas discharge of the gas displacement piping section and a float valve coupled between the gas discharge and the vacuum pump.
 8. The system of claim 1, further comprising a centrifugal pump, where the gas displacement piping section is coupled downstream of the centrifugal pump to an output of the centrifugal pump
 9. The system of claim 8, further comprising a vacuum pump fluidly coupled with the gas discharge of the gas displacement piping section and a float valve coupled between the gas discharge and the vacuum pump.
 10. The system of claim 1, where the gas displacement piping section increases in cross-sectional area from the inlet to the outlet.
 11. The system of claim 1, where the inlet and the outlet of the gas displacement piping section are smaller in cross-sectional area than the intervening region.
 12. The system of claim 1, where the gas discharge includes a plurality of elongate openings oriented perpendicular to a direction of liquid flow through the gas displacement piping section.
 13. The system of claim 1, where the gas discharge includes a plurality of elongate openings oriented parallel to a direction of liquid flow through the gas displacement piping section.
 14. The system of claim 1, where the gas discharge includes a plurality of elongate openings oriented at an angle to a direction of liquid flow through the gas displacement piping section.
 15. A liquid transport system, comprising: a centrifugal pump; a motor configured to drive an impeller of the centrifugal pump; a gas displacement piping section fluidly coupled to the centrifugal pump, including an inlet, an outlet and a gas discharge located between the inlet and the outlet for enabling gases to escape or be displaced from the gas displacement piping section, the gas displacement piping section being configured to cause entrained gases in flowing liquid to migrate toward the gas discharge; a vacuum pump fluidly coupled to the gas discharge and operative to facilitate withdrawal of gas from the gas displacement piping section; and a float valve coupled between the gas discharge of the gas displacement piping section and the vacuum pump.
 16. The system of claim 15, where the gas displacement piping section is fluidly coupled to an input of the centrifugal pump.
 17. The system of claim 16, where in a region of the gas displacement piping section containing the gas discharge, a cross-sectional area of such region is larger than a cross-sectional area of the inlet of the gas displacement piping section.
 18. The system of claim 16, where the gas displacement piping section increases in cross-sectional area from the inlet to the outlet.
 19. The system of claim 16, where the gas displacement piping section has an intervening region between the inlet and the outlet having a cross-sectional area that is larger than a cross-sectional area at the inlet and the outlet.
 20. The system of claim 16, where the gas discharge includes a plurality of elongate slots formed in a wall of the gas displacement piping section.
 21. The system of claim 20, where plural elongate members are arranged across the elongate slots to create a plurality of openings, the openings being sized to permit gas displacement while inhibiting escape of debris through the gas discharge.
 22. The system of claim 20, where the elongate slots are oriented perpendicular to a direction of liquid flow through the gas displacement piping section.
 23. The system of claim 20, where the elongate slots are oriented parallel to a direction of liquid flow through the gas displacement piping section.
 24. The system of claim 20, where the elongate slots are oriented at an angle to a direction of liquid flow through the gas displacement piping section.
 25. The system of claim 20, where plural elongate debris bars are disposed inside the gas displacement piping section over the elongate slots so as to create a mesh arrangement that permits gas displacement while inhibiting escape of debris through the gas discharge.
 26. The system of claim 15, where the gas displacement piping section is fluidly coupled to an output of the centrifugal pump.
 27. The system of claim 15, where the gas displacement piping section includes a plurality of inwardly-extending vanes configured to enhance migration of entrained gases toward the gas discharge. 